MX-3.com

I got a compression test today and i had a straight across the board in all cylinders 130lbs.
2 Questions...

1.) What was the stock compression (lbs)?

2.) What should a 94 roughly be at over time (lbs)?

Thanks.

mine, 1994 K8, has 205 psi on all 6. Spec is 195 psi brand new.

Hard to believe, but my engine has 197 000km , but has been really well maintained.

Make sure you do not have leaks on the gauge, and remember the minimum is 140 psi.

are you doing the compression test right?

you have to crank it over until you get the maximum reading on the guage. not just a couple of times like it says in a lot of manuals.

I remember someone else having this problem a while ago....hey hec

my k8 before i bent a valve due to a mis-shift at 110,000 miles pulled 155-165 between the cylinders. you only ever see it in 195-205 territory as in jm1ec-v6' case is if you have high carbon buildup from piston rings leaking on valve seals, also when you take out the spark plug and it's sopping with oil from our great valve cover grommets leaks into the cylinder with oil causing a much greater compression ration, also REMEMBER to disable your fuel to the rail by unplugging both of the connectors to the fuel rail, that can also cause skewed numbers.

So then should i be worried about having 130-135PSI ?

I would double check your numbers as I mentioned earlier.

if they are all the same, and still low, chances are, that you did it wrong.

usually only one or two cylinders are bad, not all of them.

7

se7en wrote:I would double check your numbers as I mentioned earlier.

if they are all the same, and still low, chances are, that you did it wrong.

usually only one or two cylinders are bad, not all of them.

7

Not true, the numbers make since if you take in account the age of the engine and the fact that there is an extreme amount of carb build up in the engine basing it off its age and mileage

sorta true.....it would take a lot of CAREFUL miles to wear every cylinder the same way though.....

I rebuild engines for a living, and i don't see it very often.

usually 1 or 2 are way worse.

but you're right... it could just be from wear.

7

Well i mention this because i get terrible speed up hills and when i reach the top of a hill i get my engine light and a burning smell happen. So i did a compression test and basicly iv gone through all kinds of things and now im onto to much oil cause my oil *on dipstick* is over Full so i figure thats the reason of the smell and the alot of oil in my MAF and exhaust... Any ideas?

Resolve that issue before moving on. Then get back to us.

my compression is like 100ish. car has 320k lol and it still runs 16.7-16.9 over and over.. lol

Well i changed the oil and its at a reasonable level but yet i went up the same hill i always do, went slow... Engine Light and the Smell *Not as bad but still smelt it*
So im gonna scan it soon and find out what that damn engine light means... I think its either the MAF or O2 Sensor but we shall see...

stereoking15 wrote:my k8 before i bent a valve due to a mis-shift at 110,000 miles pulled 155-165 between the cylinders. you only ever see it in 195-205 territory as in jm1ec-v6' case is if you have high carbon buildup from piston rings leaking on valve seals, also when you take out the spark plug and it's sopping with oil from our great valve cover grommets leaks into the cylinder with oil causing a much greater compression ration, also REMEMBER to disable your fuel to the rail by unplugging both of the connectors to the fuel rail, that can also cause skewed numbers.

Actually on a perfect K8 the compression should be between 190-200psi.....

And whatever you are talking about valve stem seals is funny. They have nothing to do with compeession because the valve is closed on the compression stroke. Carbon is not caused by oil from leaky piston rings as well.

My K8 is 185 +/- 1 @ 130K miles. Runs strong!

carbon is not a by prodct of gasoline, it is caused from oil, so... you dont believe that leaking valve seals play a role in compression? explain why then when they go bad that by vaccum oil is sucked into the combustion chamber? if oil seeps into the piston surface area at all it causes false readings! because the oil is sealing the rings! thus causing a mis reading of false compression! doesnt matter if the oil is coming from a valve seal or worn rings carbon only comes from oil!